Methyl-tertiary-butyl-ether (MTBE) misclassified

Methyl-tertiary-butyl-ether (MTBE) was introduced into motor fuels in 1992 to reduce carbon monoxide automotive emissions in areas where the National Ambient Air Quality Standards for CO were exceeded. At a meeting of the National Toxicology Program's Board of Scientific Counselors (2-3 December 1998), data were presented showing that exposure to MTBE caused increased incidence of liver tumors, renal adenomas, carcinomas and interstitial cell adenomas of the testes in male, and lymphomas and leukemia in female CD1 mice [National Toxicology Program, 1998]. Despite this evidence, the NTP Board defeated a motion to list MTBE as "Reasonably anticipated to be a human carcinogen" by a vote of 6 to 5. This decision directly contravenes rules and procedures previously established by NTP for assessing carcinogenicity of chemical compounds. Good public health policy dictates that the NTP Board conduct another review of MTBE with proper consideration of the criteria that have been established for listing agents as carcinogens. Millions of Americans who are exposed daily to this chemical deserve an unbiased evaluation of carcinogenic agents being introduced into the environment.